In order to meet the application requirements of high-precision and high-resolution inspection of aerospace thin-wall aluminum alloy stir welding welds, ultrasonic array testing using total focusing method was studied. The array ultrasonic testing system was built based on the multi-reflection full focus optimization algorithm of shear wave coupled with oblique wedges. The comparative test of phased array ultrasonic testing by sector scanning and array ultrasonic testing by total focusing method for the Φ0.35 mm transverse holes at different positions of the 6mm friction stir welding seam were carried out by using the developed array ultrasonic testing system. The test results show that both methods can effectively detect the transverse holes in the weld center or heat affected zone, but array ultrasonic testing by total focusing method has more advantages in signal-to-noise ratio and longitudinal resolution, which can more effectively distinguish the three holes which are 1 mm、3 mm and 5 mm from the surface in the center of the weld, and the measured signal-to-noise ratio of three holes are higher than 20dB.The development of this technology provides a new way to solve the problems of high precision, high score rate and high reliability detection of complex components in aerospace field.